The effect of intravenous nitroglycerin in patients with acute myocardial infarction has been evaluated. Nitroglycerin has been shown to improve left ventricular function and decrease the sum of ST segments obtained by precordial ST segment mapping. The addition of phenylephrine to a constant nitroglycerin infusion does not appear to be beneficial. Animal experiments have shown that coronary vasodilation with new selective maximal coronary vasodilators may increase flow to acutely infarcted regions suggesting a role for these agents in future patient studies. In addition nitroglycerin has been shown to increase the threshold of ventricular fibrillation in nonischemic animals. Studies in patients with cardiac arrest have allowed better definition of the parameters necessary for effective closed chest massage with mechanical compressives. Experimental animal studies have defined the metabolic derangements during cardiac arrest and are being used to evaluate the effect of therapeutic interventions during cardiac arrest. Coronary arteriography in patients recovering from acute myocardial infarction is being used to determine the natural history of patients with acute myocardial infarction in relation to their extent of coronary artery disease. A random trial of medical vs surgical therapy is being continued in patients with unstable angina. Noninvasive radioactive tracer techniques have been developed which show promise of eliminating the need for postoperative cardiac catheterization in patients undergoing coronary artery bypass graft surgery. Pathologic studies in these patients are defining the mechanism of graft closure. An animal model has been developed to study the effects of therapeutic interventions during transmyocardial ischemia employing intramyocardial measurement of pCO2 and pO2 by mass spectrometry. BIBLIOGRAPHIC REFERENCES: Rouleau, J., Griffith, L., Strauss, H.W., Pitt, B.: Detection of diffuse coronary artery disease by quantification of thallium 201 myocardial images. Circulation Suppl 2, 51-52, 111, 1975. Strauss, H.W., Pitt, B.: Non-invasive detection of subcritical coronary lesions by the combination of coronary vasodilatation and thallium 201 myocardial perfusion imaging. Circulation Suppl 2, 51-52, 245, 1975.